A comprehensive look at the most widely employed carbon-based electrode materials and the numerous electroanalytical applications associated with them.A valuable reference for the emerging age of carbon-based electronics and electrochemistry, this book discusses diverse applications for nanocarbon materials in electrochemical sensing. It highlights the advantages and disadvantages of the different nanocarbon materials currently used for electroanalysis, covering the electrochemical sensing of small-sized molecules, such as metal ions and endocrine disrupting chemicals (EDCs), as well as large biomolecules such as DNA, RNA, enzymes and proteins.* A comprehensive look at state-of-the-art applications for nanocarbon materials in electrochemical sensors* Emphasizes the relationship between the carbon structures and surface chemistry, and electrochemical performance* Covers a wide array of carbon nanomaterials, including nanocarbon films, carbon nanofibers, graphene, diamond nanostructures, and carbon-dots* Edited by internationally renowned experts in the field with contributions from researchers at the cutting edge of nanocarbon electroanalysisNanocarbons for Electroanalysis is a valuable working resource for all chemists and materials scientists working on carbon based-nanomaterials and electrochemical sensors. It also belongs on the reference shelves of academic researchers and industrial scientists in the fields of nanochemistry and nanomaterials, materials chemistry, material science, electrochemistry, analytical chemistry, physical chemistry, and biochemistry.

EditorsSabine Szunerits is Professor in Chemistry at the University Lille 1, France.Rabah Boukherroub is Director of research at the CNRS, Institute of Electronics, Microelectronics and Nanotechnology, France.Alison Downard is Professor of Chemistry at the University of Canterbury, Christchurch, New Zealand.Jun-Jie Zhu is Professor in the School of Chemistry and Chemical Engineering at Nanjing University, Nanjing, China.

Cover

Title Page

Copyright

Contents

List of Contributors

Series Preface

Preface

Chapter 1 Electroanalysis with Carbon Film-based Electrodes

1.1 Introduction

1.2 Fabrication of carbon film electrodes

1.3 Electrochemical performance and application of carbon film electrodes

3Graduate School of Pure and Applied Sciences, University of Tsukuba, Ibaraki, Japan

4Chiba Institute of Technology, Japan

1.1 Introduction

As electrode materials for analytical applications, carbon-based electrodes have been widely employed as detectors for high performance liquid chromatography (HPLC), capillary electrophoresis (CE) and various biosensors. Carbon materials usually shows wider potential window compared with those of novel metals such as platinum and gold electrode. These electrodes are chemically stable, highly conductive and low cost. A recent review article has well described the electrochemistry of certain carbon-based electrodes [1]. Glassy carbon (GC) and highly oriented pyrolytic graphite (HOPG) have been traditionally utilized for various electroanalytical methods. Later, carbon paste electrodes have been used mainly to develop enzymatic biosensors because carbon paste is low cost and the electrode can be fabricated only by printing and various biomolecules can be modified only by mixing with carbon ink.

In the last 20 years, electrochemical measurements using boron-doped diamond (BDD) electrodes have become more intensively studied by many groups [2-4]. A BDD electrode shows extremely wider potential window due to its chemical stability and lower background noise level than other electrode materials. Due to such unique performances, BDD electrodes are advantageous in terms of detecting various species including heavy metal ions (Pb2+, Cd2+) [5], chlorinated phenols [6], histamine and serotonin [7, 8], and even nonmetal proteins [9]. The BDD electrodes have also been employed to fabricate modified electrodes including As3+ detection with iridium-implanted BDD [10], DNA modified BDD [11] and cytochrome c modified BDD [12]. In spite of excellent performance of BDD electrodes, high temperature between 400-700° C is needed for BDD fabrication, which limits the substrates only to inorganic materials such as silicon wafer, metals and glass plate.

More recently, nanocarbon materials including carbon nanotubes (CNTs), carbon nanofibers (CNFs) and graphene nanosheet have been more intensively studied with a view to using them as electrode materials for fuel and biofuel cells [13-15]. For electroanalytical application CNT and graphene have been employed to fabricate various biosensors because nanocarbon electrodes have large surface area suitable to immobilize large amount of enzymes and antibodies [16-20]. The surface area of such nanocarbon film with immobilizing large amount of biomolecules can achieve sufficient sensitivity and longer stability. More recently, the graphene was modified onto interdigitated array electrode and applied for electrochemical immunoassay [21].

In spite of some works using nanocarbons as film electrode, the nanocarbon materials have been mainly used by modifying them on the solid electrode and larger surface area of nanocarbons also show large capacitive and background currents and reduce signal to noise (S/N) ratio when detecting trace amount of analytes.

In contrast, carbon film electrodes have been used for direct measurement of electroactive molecules such as neurotransmitters and nucleic acids. Various kinds of carbon film materials have been developed using various fabrication processes including pyrolysis of organic films, sputter deposition, chemical vapor deposition. However, carbon film electrodes are needed to improve the electron transfer rate of analytes in order to retain diffusion-limited electrochemical reactions because their smooth surface has fewer active sites than the surfaces of nanocarbon materials. Therefore, it is required to fabricate carbon films with better electroactivity. Another important advantage is that carbon film can be patterned to any shape and size with high reproducibility for use as platforms for chemical or biochemical sensors by utilizing conventional photolithographic process [22]. In this chapter, the fabrication processes of carbon film electrodes are introduced. Then, we described structure and electrochemical properties of various carbon film electrodes. Finally, we describe the application of carbon film electrodes for electroanalysis of mainly biomolecules.

1.2 Fabrication of carbon film electrodes

In order to fabricate carbon film electrodes, the pyrolysis of organic films including various polymers and deposited aromatic compounds have been employed by many groups as summarized in Table 1.1.

Kaplan et al. deposited 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTDA) films on the substrate, pyrolyzed them above 700° C and obtained conducting carbon film [23]. The conductivity was comparable to that of a GC electrode. Rojo et al. obtained carbon film using a similar method to Kaplan et al. and employed it for electrochemical measurements of catechol and catecholamines [24]. Tabei and Niwa et al. employed this process to microfabricate interdigitated array electrodes by lithographic technique [25].

The conducting polymers are also suitable to make highly conducting carbon film because the film already has p-conjugated structure. Tabei et al. used poly(p-Phenylene Vinylene):PPV coated on the substrate and prepared carbon film electrode by the pyrolysis at 1100° C, then fabricated to microdisk array electrode [26]. The carbon films have been fabricated by pyrolyzing conventional polymers. Positive photoresist, which mainly consist of phenol resin was used as precursor polymer and pyrolyzed the film at high temperature because positive photoresist can be easily spin-coated into uniform films [27]. The resistivity was between 2 × 10-2 to 2 × 10-3 O cm depending on the pyrolysis temperature. The electrochemical performance of pyrolyzed photoresist films (PPF) has been intensively studied by McCreery and Madou's groups [28, 29]. PPF film has a lower O/C ratio than a GC electrode and relatively larger peak separations were observed from the voltammograms of Fe3+/2+ and DA. The carbon film obtained by photoresist has very smooth surface. In fact, Ranganathan et al. observed that the average roughness is less than 0.5 nm by the atomic force microscopy (AFM) measurement of PPF carbon film. The modification of PPF film by diazonium reduction was performed by Brooksby et al. [30]. The modification of such carbon films is very important to use them as platforms of various electrochemical biosensors. More recently, the relationship between fabrication processes of PPF such as types of resists, and heating programs, and their resistivity and surface roughness, were well summarized by Compton's group [31]. Morita et al. carbonized polyimide (PI) film and fabricated IDA electrode [32]. The height of the electrode is ranging from 0.1 to 4.5 µm since PI is suitable to obtain thicker film.

On the other hand, carbon film electrodes have been developed by using various vacuum deposition techniques including magnetron or radio frequency (RF) or electron cyclotron resonance sputtering deposition, electron beam evaporation, plasma-assisted chemical vapor deposition (PACVD), radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD). Most well known carbon film is diamond like carbon(DLC), which is very widely used for coating of drills and cutting tools because DLC is extremely hard. Smooth and inert surface of DLC is also suitable to improve biocompatibility and applied for the coating of medical devices. A Ternary phase diagram of amorphous carbons...